I realise I can't expect the range of a more recent version of the Etherwave but I can ony get 1200Hz maximum when touching the aerial to get a higher pitch would mean turning the slug of L6 more anticlockwise, I can't do this as its at the top of its range and touching the top of the case. I've tuned L5 and L6 as per Big Briar's pdf : 'Understanding, and hot-rodding Your Etherwave Theramin'

Has anyone any advice , ideas, views? - the pdf says I should be able to get up to 5kHz. BTW Dewster's board doesn't seem to reduce the the top end range as I've tried bypassing the buffer circuitry and the top end is still severely limited

The EW is IMO notoriously difficult to tune. Marekbuk, do you have access to an oscilloscope? Setting a scope lead near the pitch antenna and tuning for the VFO tank inductor for maximum voltage will generally get you in the ballpark. I clip a short piece of wire to the scope lead to aid pickup, and keep it several inches away from the base of the antenna so as not to overly influence the operation of the EW. Thierry can help you from there.

My only (slight) concern is your use of screened cable - this will form a temperature dependent capacitor that could give a SMALL additional drift (only small - its at quite an insensitive point from the reference oscillator).. Also, the screen is a "ground wire" with large surface area, and care must be taken over the route it runs or it could affect more critical (sensitive) signals elsewhere.

I tend to use extremely fine enameled copper wire (the stuff one uses to wind coils) for these kind of signals, as this has low capacitive coupling to anything else. I almost never use screened cable at the HF end. My advice would be to replace the screened cable with the thinnest wire you can find / use!

The EW is IMO notoriously difficult to tune. Marekbuk, do you have access to an oscilloscope? Setting a scope lead near the pitch antenna and tuning for the VFO tank inductor for maximum voltage will generally get you in the ballpark. I clip a short piece of wire to the scope lead to aid pickup, and keep it several inches away from the base of the antenna so as not to overly influence the operation of the EW. Thierry can help you from there.

Yes I have a scope - so to be clear the scope is picking up the oscillator signal but without being actually clipped to a physical point on the pcb? And picks up via the short wire?

My only (slight) concern is your use of screened cable - this will form a temperature dependent capacitor that could give a SMALL additional drift (only small - its at quite an insensitive point from the reference oscillator).. Also, the screen is a "ground wire" with large surface area, and care must be taken over the route it runs or it could affect more critical (sensitive) signals elsewhere.

I tend to use extremely fine enameled copper wire (the stuff one uses to wind coils) for these kind of signals, as this has low capacitive coupling to anything else. I almost never use screened cable at the HF end. My advice would be to replace the screened cable with the thinnest wire you can find / use!

Fred.

Thanks for the advice - I will replace the screened cable on Monday when I return to work - I have some thin enamelled wire.

"Yes I have a scope - so to be clear the scope is picking up the oscillator signal but without being actually clipped to a physical point on the pcb? And picks up via the short wire?" - Marekbuk

Yes, the voltage swing is quite high at the antenna so you'll be able to clearly see a sine wave on your scope by just bringing the probe within a few inches of the base of the antenna. A bit of wire on the probe helps with the pickup.

You could use something like 24 gauge pre-tinned bus wire to make the internal connection. You want something that is small in diameter so the capacitance is low, yet rigid and solid enough not to vibrate and produce microphonics or otherwise move around.

I replaced the screened cable with some 0.5mm enamelled wire, had a go with the scope but couldn't see the signal clearly enough to detect a max level of the oscillator. In the end I screwed down L5 and L6 fully clockwise and started from there. What a difference - before I was trying to tune when they were near the top of the inductor cases but now I can get a massive range max'ing out at around 3.5khz when touching the aerial.

I'm a happy 'bunny' - thanks for the advice guys, all I've got to do now is learn to play the 'beastie' :-)